Refrigerators, freezers and other insulated cabinets are typically provided with insulated doors. These doors are usually constructed of an outer panel and an inner liner with a foam insulation between them. There are many possibilities of the type of materials used for the door panels and the method in which they are assembled and insulated. The most typical construction involves a metal fabricated exterior door shell that is formed with rear flanges on the back side to support and possibly attach a thermoformed plastic interior panel, as well as to support an extruded plastic gasket with internal magnet to seal against the cabinet. The typical insulation material is usually a polyurethane foam which is introduced into the door in three basic approaches: laminated in the exterior shell up to the rear flanges, injected into a small opening of a preassembled door, or poured into one half of the door assembly and foamed-in-place (FIP) when the outer door half is clamped down before the foam begins to expand and cure.
There are several other ways to provide a door assembly design to either reduce manufacturing complexity, improve the energy performance, improve the quality of the sealing to the cabinet, or create a unique appearance for the eye of the customer. One example of a different design approach is detailed in U.S. Pat. No. 4,053,972. It discloses special S-shaped metal retainer strips to interconnect the exterior and interior panels during the injection foaming process. However, it is apparent that the exterior door shell is still a basic metal shell which incorporates a formed rear flange (18) to attach the S-strips.
U.S. Pat. No. 5,306,082 discloses a blow-molded plastic door construction for the exterior and interior panels combined, which requires an injection foaming process. Although this approach eliminates the need for a rear flange, there are many additional concerns, such as the method of attaching the gasket seal, trimming the blow-molded edges for customer appeal, limited details for attachment of interior shelves, and the effects of thermal bow due to the temperature differential between the inside and outside of the door assembly, to name a few.